From: AugustQ
Date: February 27 2011 7:54pm
Subject: condition pushdown
List-Archive: http://lists.mysql.com/internals/38254
Message-Id: <1298836494.9127.1.camel@AMD4>
MIME-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Hi,
how can I enable condition pushdown?
This is my first question here on this list. I'm working as a
software-developer for quite some time and currently I am working in a
DWH-project here in Germany.
I found these sources: mysql-5.5.0-m2
and got it to compile and work here on my machine (Ubuntu 64bit).
After some reading (books from Hutchings/Golubchik and Pachev) I decided
to play a bit with storage engines, so I wrote my tiny storage engines
(which work, so the basics are understood, at least in parts).
The next topic I wanted to play with is condition pushdown but I had no
luck until now.
In mysql I can do
set engine_condition_pushdown=1
and got a result OK.
When I enter
explain select * from prob_alt where rv_nr = '12345678'\G
I can only see 'using where', nothing more.
I've set a breakpoint to the following piece of code:
const COND * ha_dbf::cond_push(const COND *cond)
{
myCond = (COND *)cond;
return cond;
};
Looking at the cond-var I do not see anything meaningful, mostly
NULL-Ptrs.
I assume that condition pushdown is disabled by default. So what do I
have to do to enable it?
Should I use another version of MySQL/MariaDB instead?
Thanks
AugustQ